Carburetor



, R. J. SMITH may 2, 1957 CARBURETOR 2 Sheets-Sheet 1 Filed March 12, 1965 INVENTOR. RQBERT J. SMITH BY 'l ATTORNEY May 2, 1967 R. J. SMITH 3,317,196

CARBURETOR Filed March 12, 1965 2 Sheets-Sheet 2 INVENTOR ROBERT J. SMITH ATTO RNEY gree that fuel from the float chamber United I States Patent New Jersey Filed Mar. 12, 1965, Ser. No. 439,200 1 Claim. (Cl. 261 -23) This invention relates to carburetors and in particular to low-profile multi-stage carburetors having both primary and secondary conduits and to a novel nozzle construction particularly adapted for use in the secondary conduit.

When multi-barrel, multi-stage carburetors werefirst introduced on motorc'ars, both primary and secondary barrels were about the same size, that is, approximately the same air flow capacity. Because high cruising speeds were possible on operation of the primary barrels alone, the secondaries became useful only in this upper range of engine speeds and, accordingl the added performance of the secondaries had only a limited utility. This fact was realized by some quite early, and attempts were made to modify these carburetors to bring the seconday in at lower speeds.

As motorcar engines continued to increase in size (cubic inch displacement), the capacity of the secondaries was increased with respect to the primaries in order to match the increased breathing capacity of the larger engines. In the four barrel carburetor, this was accomplished by increasing the size of the secondaries so that each was larger than its corresponding primary. At

low engine speeds, the oversized secondaries are useless because air stream velocity is too low to pull fuel out of the secondary nozzles. Consequently, at cruising speeds for the motorcar and below, the automatic transmission was set to downshift if the throttle was opened far enough to open the secondaries. The increase in engine speed after the-downshift so .increased .the air flow velocity in the secondaries that satisfactory operation of the carburetor was obtained. The downshift, of course, increased the torque transmitted from the automatic transmission and this was accomplished by the natural increase in torque from the engine which jumped to higher speeds. These two effects acting together often caused loss of traction of the driving wheels and, in all cases, a sudden startling bump, of course, a bump in acceleration is incompatible with smooth effortless operation and obviously dangerous besides. Accordingly, the trend toward increasingly larger secondaries was arrested.

Along with the trend to increased engine size and horsepower and hence increased size of carburetor, there has been a styling trend that reduces the height of the engine compartment hood. This has necessitated the use of low-profile carburetors. As to the primary barrels of the low-profile carburetor it has usually been'possible to use conventional fuel systems and conventional main fuel nozzles. However, this has not always been possible in the much larger secondary barrels.

At the same time the float chambers or fuel-supply chambers for the carburetors have been moved further from the center of the carburetor. Thus, there is sometimes'created a situation where the carburetor can be tilted, as by parking on the side of a hill, to such a decan actually spill over into the main fuel nozzles of the secondary barrels. Still another reason for the spilling over of fuel into the fuel nozzles is the fact that secondary barrels are frequently equipped with one large air valve for controlling admission of air into both of the secondary barrels. The air valve cannot interfere with the nozzles nor can the noz zles interfere with the operation of the air valve. Ac-

3,317,196 Patented May 2, 1967 cordingly, many carburetors have been constructed where the main fuel nozzles for the secondary barrels are downwardly inclined into the secondary barrels in order to provide clearance for the large air-valve plate. With this last-described construction, it has been found that a tilt of only .11 degrees can sometimes result in supplying too much fuel to one of the secondary barrels while at the same time almost starving the other secondary barrel. This also could occur in a fast hard turn of the automobile. Of course, it would be undesirable for fuel to spill over either of the nozzles when the car is parked as this would create too rich a mixture within the carburetor.

Accordingly, it is an object of the invention to provide a carburetor construction that will allow greater tilt angles without disturbing normal fuel supply to the secondary barrels of multi-stage carburetors. It is a further object of the invention to provide a novel fuel structure of a carburetor. It is still another object of the invention to provide a nozzle construction that is not sensitive to percolation of fuel in the fuel system.

According to the invention, a multi-stage, multi-barrel carburetor is constructed with primaries which are relatively much smaller than the secondaries. The small primaries will provide a soft smooth engine response in the low-speed low-power range of the engine, while the much larger secondaries will supply the capacity for fuel engine power throughout a substantial range of engine operation. Also according to the invention, the large secondary barrels or mixture conduits are provided with downwardly inclined main fuel nozzles, which nozzles are so constructed as to permit high tilt angles. Moreover, the nozzles are so installed as to aid or facilitate the separation of vaporous fuel from liquid fuel thus providing percolation-resistant characteristics. Other objects and advantages of the invention will be apparent from an examination of the drawings, the specification, and the appended claim.

FIGURE 1 is a top-plan View of a four-barrel carburetor incorporating the invention.

FIGURE 2 is a side sectional view of the carburetor of FIGURE 1.

FIGURE 3 is a sectional view of a portion of a carburetor showing the float chamber and nozzle construction of a prior-art device.

Referring now to the drawings and in particular to FIGURES l and 2, the invention will be explained in detail. Shown generally at 10 is a carburetor having primary barrels 12 and 14 and secondary barrels 16 and 18. Each of the primary barrels is provided with a venturi cluster 21 and a main fuel nozzle 22. The primary barrels of the carburetor are provided with a common choke valve 24 attached to a shaft 26 which is freely journaled at its ends to a portion of the carburetor air horn. Attached to shaft 26 is a lever arm 28 coupled by a link 30 to another lever arm 32 which in turn is coupled to a shaft 34. The shaft 34 is a counter-shaft for actuating the choke valve and shaft 34 may be provided at itsends with any conventional choking mechanism such as a manual choke or an automatic choke. Also counter-shaft 34 may be provided with a vacuum choke break unit 36'if desired. Primary bores 12 and 14 are also provided with throttle valves indicated at 37 which valves are mounted on a throttle shaft 38 journaled The secondary side of the carburetor is provided with an air valve 54 as shown in the open position. Air valve 54 is mounted on a shaft 56 journaled into the air horn of the carburetor. Shaft 56 is also provided with a biasing spring 58 for urging the air valve to a normally closed position. The air valve is opened by pressure of air against it whenever the secondary throttles are open and the engine demands additional air and fuel.

Referring now to FIGURE 2 where the secondary portion of the carburetor is shown in section, it is seen that there are provided a pair of float chambers 60 which contain floats 62 for regulating the quantity of fuel in the float chamber. As is usual, the floats 62 are provided with actuating means for operating a needle valve to adrnit fuel as required.

Fuel from float chamber 60 flows through a passage 64 into a fuel well 66 where it rises through a bleeder tube 68. Bleeder tube 68 is provided with a plurality of air bleed holes 69 which are supplied with air through a drilled passage 70. Air entering the fuel through holes 69 aerates and partially emulsifies the fuel as it rises in the passageway 66.

A hollow tube or fuel nozzle 72 is installed, as by a press fit, in suitable holes in the body of the carburetor so as to intersect fuel well 66 and project outwardly and downwardly into each of secondary barrels 18. The downward inclination of the tube 72 provides clearance for the air valve plate 54. Each nozzle tube 72 is provided with a plug 74 to close the end thereof as shown. Each nozzle is further provided with an aperture or notch 76 which as shown is in an upper portion of the tube. It is to be understood, however, that the notch 76 could be placed elsewhere as to one side or the other or even at the bottom of tube 72 if desired. The location of notch 76 will have an effect on the tilt angle required for fuel will spill over of its own accord through the nozzle, as will be herein after explained.

Each fuel well 66 is also provided with a closure plug 77 at the top thereof and each plug is provided with a vent hole '78. Vent holes 78 serve a two-fold function. One of these functions is to serve as a siphon break to prevent fuel from siphoning over through the nozzle from the fuel well 66. Another function is to release vapors that may build up in the system. A buildup of vapors can occur when the automobile engine is hot and no fuel is being drawn through the main nozzle 72. Under these conditions fuel vaporizing in well 66 will cause percolation of the liquid portion of the fuel and under some circumstances this may cause fuel to flow through the nozzle even though there is no requirement for the same. Vent hole 78 therefore permits release of these vapors and serves as an anti-percolation device.

In the fragmentary section of FIGURE 3 there is shown in nozzle 72A of the type that has been used in some prior art carburetors. The fuel bowl is shown at an angle as would be the case if a car were parked on a hillside or similar location. In this tilted attitude, the fuel rises in the fuel well 66 to such an extent that as shown in FIGURE 3 it is beginning to spill over into nozzle 72A. The angle indicated at X is the tilt angle permissible before fuel begins to spill over. In this instance, it is approximately 11 degrees although other angles of greater or lesser amounts may occur with slight changes in spacing or geometry of the carburetor. Re-

4 ferring back to FIGURE 2 it is seen that the corresponding angle Y is much greater and as there illustrated, is about 22 degrees, or twice as much.

Another condition of automobile operation that can result in unsatisfactory nozzle operation is brought about by centrifugal forces exercised upon the fuel in the fuel bowl during sharp turns. The result is much the same as though the carburetor itself were tilted. This also is avoided through the use of the nozzle constructed according to this invention.

I claim:

A carburetor for an internal combustion engine comprising:

(a) a body having primary and secondary mixture conduits,

(b) a throttle valve and a choke valve disposed in said primary conduit,

(0) main and idle fuel supply systems for said primary conduit,

((1) a main fuel supply for said secondary conduit,

(e) a throttle valve in said secondary conduit posterior to the point of entry of said main fuel to said secondary conduit,

(f) an air valve in said secondary conduit anterior to said point of entry of main fuel, said air valve being adapted to substantially close off said secondary conduit and thereby prevent entry of air into said secondary conduit when said air valve is closed, said air valve being provided with biasing means urging said air valve to closed position, said biasing means being responsive to air flow through said secondary conduit to open an amount proportional to the flow of air,

(g) the main fuel supply for said secondary conduit comprising:

(1) a fuel bowl connected to a source of fuel and having valve means for regulating admission of fuel to said bowl,

(2) a fuel passage communicating with the fuel in said fuel bowl and with a secondary fuel nozzle,

(3) an air bleeder tube in said passage for supplying air to the fuel therein,

(4) a downwardly inclined fuel nozzle intersecting said passage and extending into said secdary conduit, said nozzle being closed at the end extending into said passage and being provided with an aperturee in the upper portion only of said nozzle extending into said passage, said aperture being located so as to permit tilt angles of about 22 degrees, the portion of said nozzle under said aperture and in said passage serving to function as a vapor separator, and an anti-percolation vent at the top of said passage for venting vapors from said passage.

References Cited by the Examiner UNITED STATES PATENTS 4/1958 Henning. 9/1962 Mick. 

